1. Field of the Invention
The present invention relates in general to the field of information handling system networks, and more particularly to a system and method for managing target resets.
2. Description of the Related Art
As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
One information handling system solution for storing and accessing data is a fibre channel storage area network (SAN) environment which interfaces information from a host information handling system through a host bus adapter (HBA), a fibre channel bus, a fibre-SCSI bridge appliance and through plural SCSI buses to multiple storage servers and clusters. In a typical fibre channel SAN, primary storage disk arrays interact through the HBA to support host device storage and access of information while tape storage drives backup the information stored on the primary storage disk arrays to recover in the event of network or device failures. For instance, multiple servers and/or clusters in a fibre channel SAN environment typically share tape devices or tape device libraries for back-up operations. Typical Fibre Channel-to-SCSI bridges make is possible to connect multiple SCSI devices to a single Fibre Channel device. The bridge presents itself as a fibre channel target with the attached SCSI devices.
One difficulty with interfacing primary storage disk arrays and tape drives within a fibre channel SAN environment is that tape drives are sequential devices that may have difficulty responding to target resets issued from a host bus adapter. In a fibre channel environment, a target reset command is a common operation for recovering from bus errors, timeouts, and misbehaving target devices such as disk and tape drives. Target reset commands issued from a host bus adapter are typically translated to bus resets initiated on FC-SCSI buses by the fibre-SCSI bridge. Target resets are generally effective for clearing error conditions of non-sequential target devices, such as disk drives, but often have adverse effects on sequential target devices, such as tape drives. Typically, a host bus adapter does not know the individual target device that causes an error and so the host bus adapter sends a target reset command to all target devices operating under a target ID, generally resulting in target reset being translated into a bus reset for each FC-SCSI bus interfaced with a SCSI bridge. If multiple target devices associated with a SCSI bridge operate under the same target ID, each target device is typically subjected to a bus reset. Primary storage disk arrays are generally able to recover from target reset commands with or without input/output in progress by relying on error recovery techniques in the host bus adapter and host application. However, sequential devices may have difficulty recovering target resets while conducting input/output operations with a target reset often causing the reset of mode parameters on tape devices, the release of SCSI reservations on targets and the altering of block position on media during read and write operations. Target resets on sequential devices have an unnecessarily severe impact when the sequential devices were not misbehaving or in need of a reset. One available solution for avoiding such destructive resets is to mask target resets from reaching sequential target devices by filtering target resets from being sent by the appliance to target devices associated with a sequential target device peripheral ID. However, masking of target resets prevents both unnecessary and necessary sequential device resets.